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<Title>Track Box with Floating Legend</Title>
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<p class="heading0">ChartDirector 7.0 (Java Edition)</p>
<p class="heading1">Track Box with Floating Legend</p>
<hr class="separator">
<div class="content"><img src="images/trackbox_web.png" width='505' height='365'><br><br>
This sample program demonstrates a track cursor programmed with the following features:<br><br>
<ul>
<li>A box that horizontally centers around the x data value nearest to the mouse cursor.<br><br>
<li>A floating legend box that moves with the mouse cursor, displaying the data values at the x data value nearest to the mouse cursor.<br></ul>
On the server side, the code draws the chart as usual, and outputs both the image and the <a href="jschartmodel.htm">Javascript Chart Model</a> of the chart.<br><br>
The <b>trackBoxLegend</b> Javascript function is the routine that draws the track cursor. Its key elements are:<br><br>
The <b>trackBoxLegend</b> Javascript function is the routine that draws the track cursor. Its key elements are:<br><br>
<ul>
<li>The code first uses <a href="JsChartViewer.hideObj.htm">JsChartViewer.hideObj</a> to clear the previous track cursor, if any.<br><br>
<li>The nearest x data value is obtained using <a href="JsXYChart.getNearestXValue.htm">JsXYChart.getNearestXValue</a>.<br><br>
<li>The code draws a rectangle that horizontally spans from (x - 0.5) to (x + 0.5) with <a href="JsChartViewer.showTextBox.htm">JsChartViewer.showTextBox</a>. The +/- 0.5 offset is the suitable value to use for a label based x-axis (that is, for axis set up with <a href="Axis.setLabels.htm">Axis.setLabels</a> or <a href="Axis.setLabels2.htm">Axis.setLabels2</a>). For this type of axis, the label distance is assumed to be 1 x-axis unit irrespective of what are the labels, so an offset of 0.5 refers to the middle position between two labels.<br><br>
<li>The code then iterates through all data sets in all layers to find all the data points at the nearest x data value. For each of these points, it formats a legend entry for the point, which consists of a colored square as the icon (creating using <a href="JsChartViewer.htmlRect.htm">JsChartViewer.htmlRect</a>), data set name (obtained using <a href="JsDataSet.getDataName.htm">JsDataSet.getDataName</a>), and the data value (obtained using <a href="JsDataSet.getValue.htm">JsDataSet.getValue</a>).<br><br>
<li>Finally, the code combines all the legend entries into a legend box and draws it near the mouse cursor using <a href="JsChartViewer.showTextBox.htm">JsChartViewer.showTextBox</a>.<br></ul>
</div><p class="heading1a">Source Code Listing</p><div class="content">
<b>[JSP Version]</b> jspdemo/trackbox.jsp
<div class='codeblock'><code class='pre'>&lt;%@page import="ChartDirector.*, java.util.*" %&gt;
&lt;%
// The data for the bar chart
double[] data0 = {100, 125, 245, 147, 67};
double[] data1 = {85, 156, 179, 211, 123};
double[] data2 = {97, 87, 56, 267, 157};
String[] labels = {"Mon", "Tue", "Wed", "Thur", "Fri"};

// Create a XYChart object of size 540 x 375 pixels
XYChart c = new XYChart(540, 375);

// Add a title to the chart using 18pt Times Bold Italic font
c.addTitle("Average Weekly Network Load", "Times New Roman Bold Italic", 18);

// Set the plotarea at (50, 55) and of 440 x 280 pixels in size. Use a vertical gradient color from
// light blue (f9f9ff) to blue (6666ff) as background. Set border and grid lines to white (ffffff).
c.setPlotArea(50, 55, 440, 280, c.linearGradientColor(0, 55, 0, 335, 0xf9f9ff, 0x6666ff), -1,
    0xffffff, 0xffffff);

// Add a legend box at (50, 28) using horizontal layout. Use 10pt Arial Bold as font, with
// transparent background.
c.addLegend(50, 28, false, "Arial Bold", 10).setBackground(Chart.Transparent);

// Set the x axis labels
c.xAxis().setLabels(labels);

// Draw the ticks between label positions (instead of at label positions)
c.xAxis().setTickOffset(0.5);

// Set axis label style to 8pt Arial Bold
c.xAxis().setLabelStyle("Arial Bold", 8);
c.yAxis().setLabelStyle("Arial Bold", 8);

// Set axis line width to 2 pixels
c.xAxis().setWidth(2);
c.yAxis().setWidth(2);

// Add axis title
c.yAxis().setTitle("Throughput (MBytes Per Hour)");

// Add a multi-bar layer with 3 data sets
BarLayer layer = c.addBarLayer2(Chart.Side);
layer.addDataSet(data0, 0xff0000, "Server #1");
layer.addDataSet(data1, 0x00ff00, "Server #2");
layer.addDataSet(data2, 0xff8800, "Server #3");

// Set bar border to transparent. Use glass lighting effect with light direction from left.
layer.setBorderColor(Chart.Transparent, Chart.glassEffect(Chart.NormalGlare, Chart.Left));

// Configure the bars within a group to touch each others (no gap)
layer.setBarGap(0.2, Chart.TouchBar);

// Create the WebChartViewer object
WebChartViewer viewer = new WebChartViewer(request, "chart1");

// Output the chart
viewer.setChart(c, Chart.SVG);

// Output Javascript chart model to the browser to support tracking cursor
viewer.setChartModel(c.getJsChartModel());
%&gt;
&lt;!DOCTYPE html&gt;
&lt;html&gt;
&lt;head&gt;
    &lt;title&gt;Track Box with Floating Legend&lt;/title&gt;
    &lt;script type="text/javascript" src="cdjcv.js"&gt;&lt;/script&gt;
&lt;/head&gt;
&lt;body style="margin:5px 0px 0px 5px"&gt;
&lt;script type="text/javascript"&gt;

//
// Use the window load event to set up the MouseMovePlotArea event handler
//
JsChartViewer.addEventListener(window, 'load', function() {
    var viewer = JsChartViewer.get('&lt;%=viewer.getId()%&gt;');

    // Draw track cursor when mouse is moving over plotarea. Hide it when mouse leaves plot area.
    viewer.attachHandler(["MouseMovePlotArea", "TouchStartPlotArea", "TouchMovePlotArea", "ChartMove"],
    function(e) {
        this.preventDefault(e);   // Prevent the browser from using touch events for other actions
        trackBoxLegend(viewer, viewer.getPlotAreaMouseX(), viewer.getPlotAreaMouseY());
        viewer.setAutoHide("all", ["MouseOutPlotArea", "TouchEndPlotArea"]);
    });
});

//
// Draw track box with legend
//
function trackBoxLegend(viewer, mouseX, mouseY)
{
    // Remove all previously drawn tracking object
    viewer.hideObj("all");

    // The chart and its plot area
    var c = viewer.getChart();
    var plotArea = c.getPlotArea();

    // Get the data x-value that is nearest to the mouse
    var xValue = c.getNearestXValue(mouseX);

    // Compute the position of the box. This example assumes a label based x-axis, in which the labeling spacing
    // is one x-axis unit. So the left and right sides of the box is 0.5 unit from the central x-value.
    var boxLeft = Math.min(c.getXCoor(xValue - 0.5), c.getXCoor(xValue + 0.5));
    var boxWidth = Math.max(0, Math.abs(c.getXCoor(xValue + 0.5) - c.getXCoor(xValue - 0.5)) - 1);
    var boxTop = plotArea.getTopY();
    var boxHeight = Math.max(0, plotArea.getHeight() - 2);

    // Draw the track box
    viewer.showTextBox("trackBox", boxLeft, boxTop, JsChartViewer.TopLeft, "",
        "width:" + boxWidth + "px;height:" + boxHeight + "px;border:solid 1px black;");

    // Array to hold the legend entries
    var legendEntries = [];

    // Iterate through all layers to build the legend array
    for (var i = 0; i &lt; c.getLayerCount(); ++i)
    {
        var layer = c.getLayerByZ(i);

        // The data array index of the x-value
        var xIndex = layer.getXIndexOf(xValue);

        // Iterate through all the data sets in the layer
        for (var j = 0; j &lt; layer.getDataSetCount(); ++j)
        {
            var dataSet = layer.getDataSetByZ(j);

            // Build the legend entry, consist of a colored square box, the name and the data value.
            var dataColor = dataSet.getDataColor();
            var dataValue = dataSet.getValue(xIndex);
            if ((dataValue != null) &amp;&amp; (dataColor != null))
            {
                legendEntries.push("&lt;nobr&gt;" + viewer.htmlRect(7, 7, dataColor) + " " +
                    dataSet.getDataName() + ": " + dataValue.toPrecision(4) + "&lt;/nobr&gt; ");
            }
        }
    }

    // Create the legend by joining the legend entries
    if (legendEntries.length &gt; 0)
    {
        var legend = "&lt;u&gt;" + c.xAxis().getFormattedLabel(xValue) + "&lt;/u&gt;&lt;br /&gt;" + legendEntries.reverse().join("&lt;br /&gt;");

        // Display the legend at the bottom-right side of the mouse cursor
        viewer.showTextBox("legend", mouseX + 16, mouseY + 16, JsChartViewer.TopLeft, legend,
            "border:solid 1px black;background:#ffffcc;padding:3px;font:bold 11px Arial;-webkit-text-size-adjust:100%;");
    }
}

&lt;/script&gt;
&lt;div style="font-size:18pt; font-family:verdana; font-weight:bold"&gt;
    Track Box with Floating Legend
&lt;/div&gt;
&lt;hr style="border:solid 1px #000080" /&gt;
&lt;div style="font-size:10pt; font-family:verdana; margin-bottom:1.5em"&gt;
    &lt;a href="viewsource.jsp?file=&lt;%=request.getServletPath()%&gt;"&gt;View Source Code&lt;/a&gt;
&lt;/div&gt;
&lt;!-- ****** Here is the chart image ****** --&gt;
&lt;%=viewer.renderHTML(response)%&gt;
&lt;/body&gt;
&lt;/html&gt;</code></div></div><br>
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